Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$12.47	13.181%	$14.1137	$14.11	$14.10	$14.10
Purchase #2	$105.27	12.832%	$118.7782	$118.78	$118.80	$118.80
Purchase #3	$185.84	6.697%	$198.2857	$198.29	$198.30	$198.30
Purchase #4	$107.51	9.623%	$117.8557	$117.86	$117.85	$117.90
Purchase #5	$96.76	4.655%	$101.2642	$101.26	$101.25	$101.30
Purchase #6	$86.58	6.129%	$91.8865	$91.89	$91.90	$91.90
Purchase #7	$102.47	8.785%	$111.472	$111.47	$111.45	$111.50
7 purchase totals =	$696.90		$753.6560	$753.66	$753.65	$753.80